Author Topic: Drive Shaft Phasing for 4V K bikes  (Read 6541 times)

Offline frankenduck

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Drive Shaft Phasing for 4V K bikes
« on: May 15, 2011, 01:04:49 PM »
It's important that the U-joints on the 4 valve K bikes are in phase.  How important?  I'm not sure but it certainly can't hurt. 

The objective is to put the drive shaft together so that the drive shaft U-joints are aligned with each other as pictured in the parts catalog:


Proper drive shaft phasing reduces the stress and strain on the U-joints and reduces vibration.  If you line up the two halves of the drive shaft, you'll notice they are about one half tooth from being able to be perfectly aligned.  This is because the front half of the drive shaft has some rubber that insulates the front and rear parts of the drive shaft.  Phase the two halves of the drive shaft so that when that rubber flexes under load that the U-joints will be aligned.

Disclaimer: This is not official BMW supplied information.  It is my theory on the matter after reading some things written by engineers who know about this stuff.
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